Known motors of this type often have a rotating or linearly advancing electromagnetic armature field and usually a main supply connection of between, e.g., 110 V and 380 V and 50 or 60 Hz. Conversion into direct current is also frequently employed. Synchronous motors with optional permanent or separate excitation, reluctance motors, hysteresis motors, induction or eddy current motors, stepping motors, or combinations thereof are known. A prior-art d.c. generator with a traveling magnetic wave was described in West German Offenlegungsschriften Nos. DE-OS 29,41,890 and DE-OS 29,38,379.